Ungrounded system fault line selection method utilizing zero-sequence current multiplication characteristics

Abstract

The invention discloses an ungrounded system fault line selection method utilizing zero-sequence current multiplication characteristics. The method comprises the following steps of: monitoring neutralpoint voltage of a grounded transformer and three-phase voltage values of a bus in real time, judging a size relationship between zero-sequence voltage of the bus and a protection setting value, anddetermining whether to start a single-phase grounding fault line selection device or not; collecting bus zero-sequence voltage and zero-sequence current of all lines, selecting a fault phase accordingto the relationship among the phase voltage amplitudes UA, UB and UC, and switching on a bus switch K1 of the fault phase; collecting zero-sequence currents of all lines again, judging whether the zero-sequence currents are true or not, determining whether the switch K2 is switched on or not, and inputting a resistor RN into the neutral point of the power distribution network; collecting zero-sequence currents of all lines, opening the action of the fault phase bus switch K1, collecting the zero-sequence currents of all lines again, judging whether the zero-sequence currents are true or not,and determining a fault line; and exiting the neutral point small resistor RN, and ending line selection. The problem that single-phase earth fault line selection of a neutral point ungrounded systemis difficult is solved.

Description

technical field [0001] The invention belongs to the technical field of single-phase ground fault processing of distribution network, and in particular relates to a fault line selection method of an ungrounded system utilizing the zero-sequence current multiplication feature. Background technique [0002] Most of my country's 10kV distribution network adopts the neutral point ungrounded operation mode, and the probability of single-phase ground fault accounts for more than 80% of the total distribution network faults. Reliable fault line selection is helpful to deal with faults in time. At present, the solutions are mainly divided into passive method and active method. The passive method mainly uses the change characteristics of the electrical quantity in the line after the fault to select the line, including the use of zero-sequence component line selection and transient signal line selection, etc.; it is often affected by uncertain factors such as the complex structure of t...

AI Technical Summary

Problems solved by technology

[0004] The purpose of the present invention is to provide a fault line selection method for ungrounded systems using the zero-sequence current multiplication feature, which solves the problem of difficult line selection for single-phase ground faults in ungrounded neutral systems

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